I implore you to do the following steps:

1. Set 'Kind of Project' to Downloadable

2. Select 'Add External File' (it's to the right of the 'Upload File' and 'Choose From Dropbox' buttons)

3. Change type from Executable to Source Code ( I don't think this step really matters, but just in case)

4. Copy and paste the URL for the game into the 'http://' section

Please learn to use something other than scratch and move to unity (or ur engine of choice) next time.

fun game tho :)